For nearly twenty years the Evans/Davis collaboration would reconfigure jazz's sound, leading to several recordings such as Porgy and Bess and Sketches of Spain that were often criticized as something other than jazz. But Davis kept moving forward and in the late 1950s formed a quintet with John Coltrane (tenor saxophone), Red Garland (piano), Paul Chambers (double bass) and Philly Joe Jones (drums). Later John "Cannonball" Adderley would step in to create a sextet. With this ensemble, Davis returned to his bebop roots. With his insistence on playing longer and more legato phrases, he began exploring music made with modes-a set of musical scales used during the Medieval Period that was now being explored more theoretically by composer/performer George Russell. Russell began to formulate ideas on how jazz could extend its musical resources by exploring outside the traditional major/minor systems of music. One of his most gifted students was pianist Bill Evans, who was asked to join Davis' group in what is considered to be Davis' most essential recording Kind of Blue.

The first track appearing on Kind of Blue has arguably become Miles Davis' most influential recording. "So What" is an exploration of the Dorian mode based on a 32-bar blues form that alternates between only 2 chords. The piano chords played by Evans in the opening are based on chords built from stacked fourths (rather than the traditionally tonal chords built on stacked thirds). So important are these harmonies that they have been called the "So What chords" by many musicians.